Artificial graphene combines desirable properties
Researchers from Utrecht University together with colleagues in France have produced and described a class of materials that have the electronic properties of a semiconductor combined with those of graphene. The new material is therefore interesting for a variety of applications: from transistors to ultrarapid electronics and quantum computing. FOM workgroup leaders professor Cristiane Morais Smith (also Vici laureate) and professor Daniel Vanmaekelbergh recently published this result in the new Journal Physical Review X.
Nanotechnology can be used to produce materials with structural properties that were previously inconceivable. Daniel Vanmaekelbergh produced a honeycomb structure of the conventional semiconductor cadmium selenide. The theoretical group of Cristiane Morais Smith together with the French group of Christophe Delerue subsequently showed that this configuration combines the properties of graphene with those so-called topological insulators. This development could open up an entirely new field of applications.
Topological insulator
A topological insulator is a material that is electrically insulating on the inside but conducts electricity on its edges. Furthermore, the electrons in the edges behave in a very peculiar manner: electrons with the electron spin up move in one direction , whereas electrons with the spin down move in the other direction. Moreover, neither of the so-called spin flows experience any resistance. The net electrical current is therefore zero although there is a flow of magnetic moments. Much research is currently being done into the possibilities of using such spin flow for magnetic data storage, for example in hard disks.
Graphene
Graphene is a single layer of carbon atoms in a honeycomb structure. In graphene , the electrons move as if they have no mass. They therefore shoot through the material with the speed of light. Graphene is a highly promising material for new ultrarapid electronics. Transistors, however, cannot be made from graphene because this material always conducts current. For a transistor you need to use a semiconductor, a material in which you can switch the electrical conductance on and off.
Combination
The new combination of the apparent massless behaviour of electrons in graphene together with the spin-specific conduction in topological insulators has made a completely new class of materials possible. These materials might be interesting for data storage, but also for a new class of transistors. Furthermore it is possible to achieve a fractional quantum spin Hall effect in the edges of the structure, which is impossible in graphene. This effect is a candidate for use in quantum computing.
Reference
Dirac Cones, Topological Edge States, and Nontrivial Flat Bands in Two-Dimensional Semiconductors with a Honeycomb Nanogeometry, E. Kalesaki, C. Delerue, C. Morais Smith, W. Beugeling, G. Allan, D. Vanmaekelbergh, Physical Review X, 4, 011010 (2014).
The article can be downloaded free of charge via http://prx.aps.org/pdf/PRX/v4/i1/e011010. The research received financial support from the FOM Foundation.
Information
For further information please contact:
Daniel Vanmaekelbergh, +31 (0)30 253 22 18
Cristiane Morais Smith, +31 (0)30 253 30 62